Lids and lid assembly kits for atomic layer deposition chambers

ABSTRACT

Apparatus for processing a substrate are provided herein. In some embodiments, a lid for a substrate processing chamber includes: a lid plate comprising an upper surface and a contoured bottom surface, the upper surface having a central opening and the contoured bottom surface having a first portion that extends downwardly and outwardly from the central opening to a peripheral portion of the lid plate and a second portion that extends radially outward along the peripheral portion of the lid plate; an upper flange extending radially outward from the lid plate; and one or more channels formed through the lid plate from the upper surface of the lid plate to the second portion of the contoured bottom surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of and claims the benefit of U.S.patent application Ser. No. 14/734,838, filed Jun. 9, 2015 which claimsthe benefit of U.S. Provisional Patent Application No. 62/151,180, filedApr. 22, 2015, both of which are herein incorporated by reference intheir entireties.

FIELD

Embodiments of the disclosure generally relate to apparatus and methodsfor atomic layer deposition.

BACKGROUND

Reliably producing submicron and smaller features is one of the keytechnologies for the next generation of very large scale integration(VLSI) and ultra large scale integration (ULSI) of semiconductordevices. However, as the fringes of circuit technology are pressed, theshrinking dimensions of interconnects in VLSI and ULSI technology haveplaced additional demands on the processing capabilities. The multilevelinterconnects that lie at the heart of VLSI and ULSI technology useprecise processing of high aspect ratio features, such as vias and otherinterconnects. Reliable formation of these interconnects is veryimportant to VLSI and ULSI success and to the continued effort toincrease circuit density and quality of individual substrates.

As circuit densities increase, the widths of interconnects, such asvias, trenches, contacts, and other features, as well as the dielectricmaterials between, decrease while the thickness of the dielectric layersremain substantially constant, resulting in increased height-to-widthaspect ratios of the features. Many traditional deposition processeshave difficulty filling submicron structures where the aspect ratioexceeds 4:1, and particularly where the aspect ratio exceeds 10:1.Therefore, there is a great amount of ongoing effort being directed atthe formation of substantially void-free and seam-free submicronfeatures having high aspect ratios.

Atomic layer deposition (ALD) is a deposition technique being exploredfor the deposition of material layers over features having high aspectratios. One example of an ALD process includes the sequentialintroduction of pulses of gases. For instance, one cycle for thesequential introduction of pulses of gases may contain a pulse of afirst reactant gas, followed by a pulse of a purge gas and/or a pumpevacuation, followed by a pulse of a second reactant gas, and followedby a pulse of a purge gas and/or a pump evacuation. The term “gas” asused herein is defined to include a single gas or a plurality of gases.Sequential introduction of separate pulses of the first reactant and thesecond reactant may result in the alternating self-limiting absorptionof monolayers of the reactants on the surface of the substrate and,thus, forms a monolayer of material for each cycle. The cycle may berepeated to a desired thickness of the deposited material. A pulse of apurge gas and/or a pump evacuation between the pulses of the firstreactant gas and the pulses of the second reactant gas serves to reducethe likelihood of gas phase reactions of the reactants due to excessamounts of the reactants remaining in the chamber.

In some chamber designs for ALD processing, precursors and gases aredelivered using a funnel lid through which precursor is distributedthrough multiple injectors above a funnel shaped lid. The injectorsgenerate a circular motion of the injected gas which distributes throughthe funnel profile at the center of the lid. The rotational inertia ofthe gas/ALD precursor molecules distributes the molecules from center toedge resulting in improved uniformity deposition. However, in someapplications, the inventors have observed a donut-shaped depositionprofile near the center of the substrate being processed. Thedonut-shaped deposition profile is believed to be caused by the funnelshape of the lid and can lead to integration issues for customers.

Therefore, the inventors have provided improved apparatus and methodsfor ALD processing of a substrate.

SUMMARY

Methods and apparatus for processing a substrate are provided herein. Insome embodiments, a substrate processing chamber includes: a chamberbody; a chamber lid assembly having a housing enclosing a centralchannel that extends along a central axis and has an upper portion and alower portion; a lid plate coupled to the housing and having a contouredbottom surface that extends downwardly and outwardly from a centralopening coupled to the lower portion of the central channel to aperipheral portion of the lid plate; and a gas distribution platedisposed below the lid plate and having a plurality of aperturesdisposed through the gas distribution plate.

In some embodiments, a substrate processing chamber includes: a chamberbody; a chamber lid assembly having a housing enclosing a centralchannel that extends along a central axis and has an upper portion and alower portion; a lid plate coupled to the housing and having a contouredbottom surface that extends downwardly and outwardly from a centralopening coupled to the lower portion of the central channel to aperipheral portion of the lid plate; a gas distribution plate disposedbelow the lid plate and having a plurality of apertures disposed throughthe gas distribution plate; a remote plasma source fluidly coupled tothe central channel; an isolation collar coupled between the remoteplasma source and the housing, wherein the isolation collar has an innerchannel extending through the isolation collar to fluidly couple theremote plasma source and the central channel; an exhaust conduit coupledto the isolation collar at a first end and to a main pumping channel ata second end; and a valve coupled to the exhaust conduit to selectivelyopen or close the exhaust conduit.

In some embodiments, a method of processing a substrate includes:flowing a first process gas into a gas dispersion channel and a reactionzone of a process chamber; flowing the first process gas through aplurality of apertures in a gas distribution plate disposed in thereaction zone and onto the substrate; flowing a cleaning gas into thegas dispersion channel and the reaction zone; exhausting the cleaninggas via an exhaust system; flowing a second process gas into the gasdispersion channel and the reaction zone; flowing the second process gasthrough the plurality of apertures in the gas distribution plate andonto the substrate; flowing the cleaning gas into the gas dispersionchannel and the reaction zone; and exhausting the cleaning gas via theexhaust system.

Other and further embodiments of the present disclosure are describedbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present disclosure, briefly summarized above anddiscussed in greater detail below, can be understood by reference to theillustrative embodiments of the disclosure depicted in the appendeddrawings. However, that the appended drawings illustrate only typicalembodiments of the disclosure and are therefore not to be consideredlimiting of scope, for the disclosure may admit to other equallyeffective embodiments.

FIG. 1 depicts a schematic view of a process chamber in accordance withsome embodiments of the present disclosure.

FIG. 2 depicts a schematic cross-sectional view of a process chamber inaccordance with some embodiments of the present disclosure.

FIG. 3 depicts a schematic cross-sectional view of a lid assembly inaccordance with some embodiments of the present disclosure.

FIGS. 4A-C depict schematic views of apertures disposed through a gasdistribution plate in accordance with embodiments of the presentdisclosure.

FIG. 5 depicts a flowchart illustrating a method of processing asubstrate in accordance to some embodiments of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. The figures are not drawn to scale and may be simplifiedfor clarity. Elements and features of one embodiment may be beneficiallyincorporated in other embodiments without further recitation.

DETAILED DESCRIPTION

Embodiments of the present disclosure provide apparatus and methods thatmay be used to clean substrate processing chambers, such as an atomiclayer deposition (ALD) chamber, and to deposit materials during, forexample, an ALD process. Embodiments include substrate processingchambers and gas delivery systems which include a remote plasma sourceand a gas distribution plate. Other embodiments provide methods fordepositing materials using these gas delivery systems during ALDprocesses. Examples of suitable processing chambers for incorporation ofthe apparatuses described herein include high dielectric constant (i.e.,high k) and metal ALD deposition chambers available from AppliedMaterials, Inc., of Santa Clara, Calif. The following process chamberdescription is provided for context and exemplary purposes, and shouldnot be interpreted or construed as limiting the scope of the disclosure.

FIG. 1 is a schematic view of a substrate processing chamber (processchamber 100) including a gas delivery system 130 adapted for ALDprocesses in accordance with some embodiments of the present disclosure.FIG. 2 is a cross-sectional view of the process chamber 100. Processchamber 100 includes a chamber body 102 having a processing volumewithin the chamber body 102 and beneath the chamber lid assembly 132.Slit valve 108 in the process chamber 100 provides access for a robot(not shown) to deliver and retrieve a substrate 110, such as a 200 mm or300 mm semiconductor wafer or a glass substrate, to and from the processchamber 100. A chamber liner 177 is disposed along the walls of theprocess chamber 100 to protect the chamber from corrosive gases usedduring processing/cleaning.

A substrate support 112 supports the substrate 110 on a substratereceiving surface 111 in the process chamber 100. The substrate support112 is mounted to a lift motor 114 for raising and lowering thesubstrate support 112 and the substrate 110 disposed on the substratesupport. A lift plate 116 (shown in FIG. 2), connected to a lift motor118, is mounted in the process chamber 100 to raise and lower lift pins120 movably disposed through the substrate support 112. The lift pins120 raise and lower the substrate 110 over the surface of the substratesupport 112. The substrate support 112 may include a vacuum chuck (notshown), an electrostatic chuck (not shown), or a clamp ring (not shown)for securing the substrate 110 to the substrate support 112 during adeposition process.

The temperature of the substrate support 112 may be adjusted to controlthe temperature of the substrate 110. For example, substrate support 112may be heated using an embedded heating element, such as a resistiveheater (not shown), or may be heated using radiant heat, such as heatinglamps (not shown) disposed above the substrate support 112. A purge ring122 may be disposed on the substrate support 112 to define a purgechannel 124 which provides a purge gas to a peripheral portion of thesubstrate 110 to prevent deposition on the peripheral portion of thesubstrate 110.

Gas delivery system 130 is disposed at an upper portion of the chamberbody 102 to provide a gas, such as a process gas and/or a purge gas, toprocess chamber 100. A vacuum system (not shown) is in communicationwith a pumping channel 179 to evacuate any desired gases from theprocess chamber 100 and to help maintain a desired pressure or pressurerange inside the process chamber 100.

In some embodiments, the chamber lid assembly 132 includes a gasdispersion channel 134 extending through a central portion of thechamber lid assembly 132. As shown in FIGS. 1 and 2, the gas dispersionchannel 134 extends perpendicularly toward the substrate receivingsurface 111 and also extends along a central axis 133 of the gasdispersion channel 134, through lid plate 170, and to lower surface 160.In some embodiments, an upper portion of the gas dispersion channel 134is substantially cylindrical along central axis 133 and a lower portionof the gas dispersion channel 134 tapers away from central axis 133. Thelower surface 160 is sized and shaped to substantially cover thesubstrate 110 disposed on the substrate receiving surface 111 of thesubstrate support 112. The lower surface 160 tapers from an outer edgeof the lid plate 170 towards the gas dispersion channel 134. The gasdelivery system 130 may provide one or more gasses to the gas dispersionchannel 134 to process the substrate 110. In some embodiments, the gasdelivery system 130 may be coupled to the gas dispersion channel 134 viaone gas inlet. In some embodiments, such as that shown in FIG. 3, thegas delivery system may be coupled to the gas dispersion channel 134 viaa plurality of inlets.

As illustrated in FIG. 3, circular gas flow 174, which illustrates theflow of process gases through the gas dispersion channel 134, maycontain various types of flow patterns. In some embodiments, processinggases may be forced to make revolutions around central axis 133 of gasdispersion channel 134 while passing through the dispersion channel. Insuch embodiments, the circular gas flow 174 may contain various types ofcircular flow patterns, such as a vortex pattern, a helix pattern, aspiral pattern, or derivatives thereof.

Although providing a circular gas flow 174 is beneficial for manyapplications, the inventors have discovered that in some applications,the circular gas flow can lead to non-uniform processing results. Theinventors have observed the gas flow may lead to a donut-shapeddeposition profile near a center of the substrate 110 being processed.The donut-shaped profile may be caused by the funnel shape of gasdispersion channel 134. Therefore, in some embodiments, the processchamber 100 further includes a gas distribution plate 125 having aplurality of apertures 126 disposed through the gas distribution plate125. The gas distribution plate 125 extends to the surface of the gasdispersion channel 134 such that the only pathway from the gasdispersion channel 134 to the substrate is through the plurality ofapertures 126 of the gas distribution plate 125. The gas distributionplate 125 advantageously creates a choked flow of gas through the gasdistribution plate 125 resulting in a more uniform deposition on thesubstrate 110 and, thus, substantially eliminating the donut-shapeddeposition caused by the rotational flow of gas.

In some embodiments, the gas distribution plate 125 is formed of anon-corrosive ceramic material such as, for example, aluminum oxide oraluminum nitride. In some embodiments, each of the plurality ofapertures 126 may have an equivalent fluid conductance. In someembodiments, a density of the plurality of apertures 126 (e.g., thenumber of apertures or the size of the openings of the apertures perunit area) may vary across the gas distribution plate 125 to achieve adesired deposition profile on the substrate 110. For example, a higherdensity of apertures 126 may be disposed at a center of the gasdistribution plate 125 to increase the deposition rate at the center ofthe substrate relative to the edge of the substrate to further improvedeposition uniformity.

Although the plurality of apertures 126 are depicted as cylindricalthrough holes, the plurality of apertures 126 may have differentprofiles. FIGS. 4A-C depict different non-limiting embodiments ofprofiles of the plurality of apertures 126. In the embodiment depictedin FIG. 4A, the aperture 126 is a cylindrical through hole having curvededges 402 that surround the aperture. In the embodiment depicted in FIG.4B, the aperture 126 is a through hole having an upper portion 404 thattapers inwardly toward a center of the aperture, a cylindrical centerportion 405 extending perpendicularly to an upper surface 127 of the gasdistribution plate 125, and a lower portion 406 that tapers outwardlyfrom the center of the aperture. In the embodiment depicted in FIG. 4C,the aperture 126 is a through hole having an upper portion 408 having acountersunk hole, a cylindrical center portion 409 extendingperpendicularly to the upper surface 127 of the gas distribution plate125, and a lower portion 410 that tapers outwardly from the center ofthe aperture. Other profiles of the plurality of apertures 126 mayalternatively be used to achieve optimal deposition uniformity duringprocessing of the substrate 110.

Not wishing to be bound by theory, the inventors believe that thediameter of gas dispersion channel 134, which is constant from the upperportion of gas dispersion channel 134 to a first point along centralaxis 133 and increasing from the first point to lower portion 135 of gasdispersion channel 134, allows less of an adiabatic expansion of a gasthrough gas dispersion channel 134 which helps to control thetemperature of the process gas contained in the circular gas flow 174.For example, a sudden adiabatic expansion of a gas delivered into gasdispersion channel 134 may result in a drop in the temperature of thegas which may cause condensation of the gas and formation of droplets.On the other hand, a gas dispersion channel 134 that gradually tapers isbelieved to provide less of an adiabatic expansion of a gas. Therefore,more heat may be transferred to or from the gas, and, thus, thetemperature of the gas may be more easily controlled by controlling thetemperature of chamber lid assembly 132. Gas dispersion channel 134 maygradually taper and contain one or more tapered inner surfaces, such asa tapered straight surface, a concave surface, a convex surface, orcombinations thereof or may contain sections of one or more taperedinner surfaces (i.e., a portion tapered and a portion non-tapered).

As shown in FIG. 3, the upper portion of the gas dispersion channel 134is defined by an insert 300 disposed in an inner region of a housing375. The insert 300 includes a cap 302 at an upper portion of the insert300 and a central passageway that at least partially defines the gasdispersion channel 134. The cap 302 extends over the housing 375 to holdthe insert 300 in place. The insert 300 and cap 302 include a pluralityof o-rings 385 disposed between the insert 300 and the housing 375 toensure proper sealing. The insert 300 includes a plurality ofcircumferential apertures which, when the insert 300 is inserted intothe housing 375, form a corresponding plurality of circumferentialchannels 360, 365, 370. The plurality of circumferential channels 360,365, 370 are fluidly coupled to the gas dispersion channel 134 via acorresponding plurality of holes 340, 345, 350. In the embodiment shownin FIG. 3, the gas delivery system 130 is coupled to the gas dispersionchannel 134 via a plurality of gas feed lines 310, 315, 320. The gasfeed lines 310, 315, 320 are fluidly coupled to the plurality ofcircumferential channels 360, 365, 370 to provide one or more gases tothe gas dispersion channel 134.

Returning to FIGS. 1 and 2, the process chamber 100 further includes achamber cleaning system including a remote plasma source (RPS) 190, anisolation collar 192 coupled to the RPS 190 at one end and the cap 302at an opposite end, a heater plate 198 coupled to an upper surface ofthe lid plate 170, and a cleaning gas (i.e., purge gas) source 197fluidly coupled to the RPS 190. The cleaning gas source may include anygas suitable for forming a plasma to clean the process chamber 100. Insome embodiments, for example, the cleaning gas may be nitrogentrifluoride (NF₃). The isolation collar 192 includes an inner channel193 that is fluidly coupled to the gas dispersion channel 134 through aplurality of holes 285 disposed in a central portion of the cap 302 toflow a plasma from the RPS 190 through the gas dispersion channel 134and into the reaction zone 164. The heater plate 198 may be formed ofstainless steel and include a plurality of resistive heating elementsdispersed throughout the plate.

Typically, a cleaning gas is flowed through the gas dispersion channel134 and the reaction zone 164 after a first gas is provided to the gasdispersion channel 134 by the gas delivery system 130 to quickly purgethe first gas from the gas dispersion channel 134 and the reaction zone164. Subsequently, a second gas is provided by the gas delivery system130 to the gas dispersion channel 134 and the cleaning gas is againflowed through the gas dispersion channel 134 to the reaction zone 164to quickly purge the second gas from the gas dispersion channel 134 andthe reaction zone 164. However, the addition of the gas distributionplate 125 chokes the flow of the cleaning gas to the pumping channel 179and prolongs the cleaning process. As such, the inventors haveincorporated an exhaust system 180 having an exhaust conduit 184 coupledto the isolation collar 192 at a first end 186 and to the pumpingchannel 179 at a second end 188. A valve 182 is disposed in the exhaustconduit 184 to selectively fluidly couple the exhaust conduit 184 to theinner channel 193. In some embodiments, for example, the valve 182 maybe a plunger type valve having a plunger 202 that is moveable between afirst position (shown in FIG. 2) to fluidly couple the exhaust conduit184 to the inner channel 193 and a second position to seal off theexhaust conduit 184 from the inner channel 193. Each time the cleaninggas is flowed through the gas dispersion channel 134 and the reactionzone 164, the valve 182 is opened and the cleaning gas is rapidlyexhausted to the pumping channel 179.

When a pressure inside of the process chamber 100 exceeds a pressureinside of the RPS 190, processing gasses may flow up to and damage theRPS 190. The plurality of holes 285 serve as a choke point to prevent abackflow of processing gases from flowing up through the inner channel193 and into the RPS 190. The isolation collar 192 may be formed of anymaterial that is non-reactive with the cleaning gas being used. In someembodiments, the isolation collar 192 may be formed of aluminum when thecleaning gas is NF₃. In some embodiments, the isolation collar 192 andthe insert 300 may be formed of aluminum and coated with a coating toprevent corrosion of the isolation collar 192 and the insert 300 fromcorrosive gases when used. For example, the coating may be formed ofnickel or aluminum oxide.

Referring to FIG. 3, the RPS 190 operates at a temperature less than orequal to about 40° C. In order advantageously insulate the RPS 190 fromheat generated in the process chamber 100, a thermal isolation ring 394is disposed between the isolation collar 192 and the cap 302. Thethermal isolation ring 394 is formed of a metal with low thermalconductivity (e.g., lower than the thermal conductivity of the isolationcollar 192 and the cap 302). In addition, an o-ring 385 may also bedisposed between the isolation collar 192 and the cap 302 to furtherreduce the contact area between the isolation collar 192 and the cap302. The combination of the thermal isolation ring 394 and the o-ring385 acts as a thermal choke to ensure that the heat generated in theprocess chamber 100 does not adversely affect the RPS 190.

In some embodiments, when the lid plate 170 is heated above 100° C. theprocess chamber 100 may include a differential pumping line 250 toensure that any process gases or byproducts trapped between o-rings 385are exhausted to the pumping channel 179. The differential pumping line250 is coupled to the lid plate 170 at a first end and to the insert 300at a second end opposite the first end. The differential pumping line isfluidly coupled to the gas dispersion channel 134 and to one or morechannels 260 formed at areas between two or more o-rings 385. When thevalve 182 is opened to exhaust the gas dispersion channel 134, thedifferential pumping line exhausts gases trapped between o-rings 385.

Returning to FIG. 3, a portion of lower surface 160 of chamber lidassembly 132 may be contoured or angled downwardly and outwardly from acentral opening coupled to the gas dispersion channel 134 to aperipheral portion of chamber lid assembly 132 to help provide animproved velocity profile of a gas flow from gas dispersion channel 134across the surface of substrate 110 (i.e., from the center of thesubstrate to the edge of the substrate). Lower surface 160 may containone or more surfaces, such as a straight surface, a concave surface, aconvex surface, or combinations thereof. In one embodiment, lowersurface 160 is convexly funnel-shaped.

In one example, lower surface 160 is downwardly and outwardly slopingtoward an edge of the substrate receiving surface 111 to help reduce thevariation in the velocity of the process gases traveling between lowersurface 160 of chamber lid assembly 132 and substrate 110 whileassisting to provide uniform exposure of the surface of substrate 110 toa reactant gas. The components and parts of chamber lid assembly 132 maycontain materials such as stainless steel, aluminum, nickel-platedaluminum, nickel, alloys thereof, or other suitable materials. In oneembodiment, lid plate 170 may be independently fabricated, machined,forged, or otherwise made from a metal, such as aluminum, an aluminumalloy, steel, stainless steel, alloys thereof, or combinations thereof.

In some embodiments, inner surface 131 of gas dispersion channel 134 andlower surface 160 of chamber lid assembly 132 may contain a mirrorpolished surface to help a flow of a gas along gas dispersion channel134 and lower surface 160 of chamber lid assembly 132.

Referring to FIGS. 1-3, in a processing operation, substrate 110 isdelivered to process chamber 100 through slit valve 108 by a robot (notshown). Substrate 110 is positioned on substrate support 112 throughcooperation of lift pins 120 and the robot. Substrate support 112 raisessubstrate 110 into close opposition to a lower surface of the gasdistribution plate 125. A first gas flow may be injected into gasdispersion channel 134 of process chamber 100 by the gas delivery system130 together or separately (i.e., pulses) with a second gas flow. Thefirst gas flow may contain a continuous flow of a purge gas from a purgegas source and pulses of a reactant gas from a reactant gas source ormay contain pulses of a reactant gas from the reactant gas source andpulses of a purge gas from the purge gas source. The second gas flow maycontain a continuous flow of a purge gas from a purge gas source andpulses of a reactant gas from a reactant gas source or may containpulses of a reactant gas from a reactant gas source and pulses of apurge gas from a purge gas source.

The circular gas flow 174 travels through gas dispersion channel 134 andsubsequently through the plurality of apertures 126 in the gasdistribution plate 125. The gas is then deposited on the surface ofsubstrate 110. Lower surface 160 of chamber lid assembly 132, which isdownwardly sloping, helps reduce the variation of the velocity of thegas flow across the surface of gas distribution plate 125. Excess gas,by-products, etc. flow into the pumping channel 179 and are thenexhausted from process chamber 100. Throughout the processing operation,the heater plate 198 may heat the chamber lid assembly 132 to apredetermined temperature to heat any solid byproducts that haveaccumulated on walls of the process chamber 100 (or a processing kitdisposed in the chamber). As a result, any accumulated solid byproductsare vaporized. The vaporized byproducts are evacuated by a vacuum system(not shown) and pumping channel 179. In some embodiments, thepredetermined temperature is greater than or equal to 150° C.

FIG. 5 illustrates a method 500 of processing a substrate in accordancewith some embodiments of the present disclosure. At 505, a first processgas is flowed from the gas delivery system 130 into the gas dispersionchannel 134 and the reaction zone 164. At 510, the first process gas isflowed through the plurality of apertures 126 in the gas distributionplate 125 and onto the substrate 110. At 515, a cleaning gas is flowedinto the gas dispersion channel 134 and the reaction zone 164 to purgethe first process gas. At 520, the cleaning gas is exhausted via theexhaust system 180. At 525 a second process gas is flowed into the gasdispersion channel 134 and the reaction zone 164. At 530, the secondprocess gas is flowed through the plurality of apertures 126 in the gasdistribution plate 125 and onto the substrate 110. At 535, the cleaninggas is flowed into the gas dispersion channel 134 and the reaction zone164 to purge the second process gas. At 540, the cleaning gas isexhausted via the exhaust system 180.

Other embodiments of a chamber adapted for atomic layer depositionincorporate one or more of these features.

While the foregoing is directed to some embodiments of the presentdisclosure, other and further embodiments may be devised withoutdeparting from the basic scope thereof.

We claim:
 1. A lid for a substrate processing chamber, comprising: a lidplate comprising an upper surface and a contoured bottom surface, theupper surface having a central opening and the contoured bottom surfacehaving a first portion that extends downwardly and outwardly from thecentral opening to a peripheral portion of the lid plate and a secondportion that extends radially outward along the peripheral portion ofthe lid plate; an upper flange extending radially outward from the lidplate; and one or more channels formed through the lid plate from theupper surface of the lid plate to the second portion of the contouredbottom surface.
 2. The lid of claim 1, wherein the upper surface of thelid plate is planar.
 3. The lid of claim 1, wherein the upper surface ofthe lid plate and the second portion of the contoured bottom surface areparallel.
 4. The lid of claim 1, further comprising: an o-ring groovedisposed in the upper surface of the lid plate surrounding the centralopening.
 5. The lid of claim 1, wherein the contoured bottom surface hasa mirror polished surface.
 6. The lid of claim 1, wherein the lid plateis fabricated from metal.
 7. The lid of claim 1, wherein the lid plateis fabricated from aluminum, an aluminum alloy, steel, or stainlesssteel.
 8. The lid of claim 1, further comprising: a gas distributionplate configured to be coupled to the lid plate such that the contouredbottom surface of the lid plate extends to and contacts the gasdistribution plate, wherein the gas distribution plate has a pluralityof apertures disposed therethrough such that the only pathway from thecentral opening to a region beneath the gas distribution plate isthrough the plurality of apertures when the gas distribution plate iscoupled to the lid plate.
 9. The lid of claim 8, wherein the gasdistribution plate is formed of a non-corrosive ceramic material. 10.The lid of claim 8, wherein the gas distribution plate is formed ofaluminum oxide or aluminum nitride.
 11. The lid of claim 8, wherein eachof the plurality of apertures have an equivalent fluid conductance. 12.The lid of claim 8, wherein each aperture of the plurality of aperturesis a through hole having an upper portion having a countersunk hole, acylindrical center portion extending perpendicularly to the uppersurface of the gas distribution plate, and a lower portion that tapersoutwardly from the center of the aperture.
 13. The lid of claim 8,wherein the gas distribution plate includes a central portion containingthe plurality of apertures, and a first stepped portion surrounding theplurality of apertures and configured to interface with the secondportion of the contoured bottom surface of the lid plate.
 14. The lid ofclaim 13, wherein the gas distribution plate further includes a secondstepped portion surrounding the first stepped portion and configured tointerface with the upper flange of the lid plate.
 15. A lid assembly kitfora substrate processing chamber, comprising: a lid plate comprising anupper surface and a contoured bottom surface, the upper surface having acentral opening and the contoured bottom surface having a first portionthat extends downwardly and outwardly from the central opening to aperipheral portion of the lid plate and a second portion that extendsradially outward along the peripheral portion of the lid plate, the lidplate having an upper flange extending radially outward from the lidplate and one or more channels formed through the lid plate from theupper surface of the lid plate to the second portion of the contouredbottom surface; and a gas distribution plate configured to be coupled tothe lid plate such that the contoured bottom surface of the lid plateextends to and contacts the gas distribution plate, wherein the gasdistribution plate has a plurality of apertures disposed therethroughsuch that the only pathway from the central opening to a region beneaththe gas distribution plate is through the plurality of apertures whenthe gas distribution plate is coupled to the lid plate, wherein the gasdistribution plate includes a central portion containing the pluralityof apertures, a first stepped portion surrounding the central portionand configured to interface with the second portion of the contouredbottom surface of the lid plate, and a second stepped portionsurrounding the first stepped portion and configured to interface withthe upper flange of the lid plate.
 16. The lid assembly kit of claim 15,wherein each of the plurality of apertures have an equivalent fluidconductance.
 17. The lid assembly kit of claim 15, wherein the gasdistribution plate is formed of a non-corrosive ceramic material. 18.The lid assembly kit of claim 15, wherein the gas distribution plate isformed of aluminum oxide or aluminum nitride.
 19. The lid assembly kitof claim 15, wherein the lid plate is fabricated from metal.
 20. The lidassembly kit of claim 15, wherein the lid plate is fabricated fromaluminum, an aluminum alloy, steel, or stainless steel.